Inhalation therapy is the medical art of treating a patient with a breathable gas (such as air, oxygen or a mixture of air and oxygen) which may or may not contain medication.
The prior art is replete with a variety of different types of inhalation-therapy devices. Some types of inhalation-therapy devices operate by combining water vapor with a humidifiable breathable gas, while other types operate by combining fine liquid water droplets (or mist) with such a gas. Yet other types of these devices operate by bubbling a humidifiable breathable gas through water, or by heating the water, to generate water vapor which is later combined with a humidifiable breathable gas.
For example, each of U.S. Pat. Nos. 4,216,176 (to Tanaka); 4,110,419 (to Miller); 3,954,920 (to Heath); 3,820,540 (to Hirtz et al.); and 1,732,674 (to Dever), discloses an air-humidifier device employing either radiant-heating means and/or convection-heating means to evaporate water from a wetted wick or the like to thereby humidify air passing therethrough, while in each of U.S. Pat. Nos. 3,982,095 (to Robinson); and 3,864,440 (to Giocoechea), air is bubbled through a heated body of water for air humidification purposes.
U.S. Pat. No. 3,809,374 to Schossow employs both conduction-heating means and convection-heating means to humidify air. Briefly, Schossow discloses a vaporizer-humidifier wherein an electrical heater is immersed into a body of water to produce water vapor. The Schossow patent teaches using mechanical mixing means to mix the thus generated water vapor with air.
One problem with inhalation-therapy devices of the various types mentioned above (except perhaps for the '540 patent to Hirtz et al.) is that each device is operative generally in only one position (i.e. only when disposed vertically or only when positioned on a horizontal surface) and will not operate when positioned on its side. The '540 device, however, poses other problems in that it requires periodic disassembly to re-wet its porous water-storage element.
A problem which arises when employing the gas-bubbler types of inhalation-therapy devices is that the bubbling of a gas through a body of water requires pressurization of the gas to overcome an inherent pressure differential presented by the body of water. Moreover, bubbler devices generally do not effectively use all water contained therewithin. Also, the rate at which heat is transferred into the body of water for water-vaporization purposes is generally inefficient and slow.
The inhalation-therapy art also includes water mist-producing devices. For example, each of U.S. Pat. Nos. 4,101,611 (to Williams); and 3,864,544 (to van Amerongen), discloses a device wherein water is first heated, then nebulized, and finally mixed with a gas that is to be humidified. Each of U.S. Pat Nos. 4,116,387 (to Kremer et al.); and 3,771,721 (to van Amerongen), however, excludes the water-heating step prior to water nebulization.
One problem experienced when a liquid water particle is introduced into an air stream for purposes of humidifying the air, of course, is the cooling effect experienced when the sensible heat of the air provides the latent heat necessary to evaporate each water particle. The humidified air may in fact be too cold for many inhalation-therapy applications.
While some of the above-discussed inhalation-therapy devices are large and cumbersome, others may operate in a complicated manner involving cooperation of a variety of mechanical, electrical, and/or electromechanical elements.
Yet another problem met when the various types of water vapor-producing and/or gas bubbler-based devices discussed above are used in connection with inhalation therapy is that it is often necessary to use sterile water in the inhalation therapy device. Use of sterile water, currently costing as much as several dollars a quart, thus becomes an economic consideration. It would be desirable to be able to use a less costly form of relatively clean water for purposes of inhalation therapy.
The humidifier assembly of the present invention minimizes the drawbacks of the aforementioned prior art humidifiers and provides an apparatus that is reliable and relatively inexpensive to use.